The present invention relates to a connector for printed circuit boards, and particularly to a connector fixed to a daughter board which mates with surface contacts on a mother board.
Printed circuit boards in the form of daughter cards are pluggably connected to mother boards to allow ready replacement of the cards or expansion of a system. Connection is generally provided by card-edge type connectors which are fixed to the mother board and contact pads on an inserted daughter card directly, as shown in U.S. Pat. No. 3,397,381, or by means of a two-piece arrangement where a connector fixed to the daughter card having contacts therein which mate with contacts in a connector fixed to a mother board. This is exemplified by U.S. Pat. No. 3,864,000, wherein right angle pins mounted in a housing and soldered into holes in a daughter card are mated with socket members mounted in a housing and soldered into holes in a mother board. Recently the two-piece arrangement has become more popular since the board-to-board pinout density of a card edge connector is limited by the linear space available on the edge of the daughter board, allowing increased contact density only by reduced pad width and closer centerline spacing. The result is increased potential for mismating, which would necessitate tighter manufacturing tolerances on both boards and connectors, which tolerances are not economically realistic. Two-piece connectors are not limited in the same fashion since more rows of contacts can be added. Using the circuit board edge for the connection also causes problems associated with warpage, variations in board thickness, and the 0.062 inch thickness limitation imposed by standard card-edge connector design. Two piece connectors, while solving some of the above problems, are inherently more expensive. Either of the common prior art arrangements requires a connector with contacts therein which are received in through holes in the mother board. Systems are often sold with these connectors attached to the mother boards where the daughter cards are only to be optionally provided in the event the system is expanded. Thus, where daughter cards are not ultimately used, unnecessary cost of holes and connectors is suffered. In any event, it would be desirable to provide an arrangement where connectors fixed to a daughter card could make electrical contact with surface contacts on a mother board. This would cost less than providing connectors on the mother board and would provide the same advantages over card edge technology as two-piece connectors.
The surface contact arrangement dictated by the above considerations would necessarily require aligning means on the mother board and further would require resilient compliance of contact elements with surface contacts on the mother board. Additionally, wiping action during contact engagement is desirable as in any contact mating.